<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <script type="text/javascript">
        {
            var a = 2;
            alert("duguqingyan");
            console.log("独立");
        }
        console.log("a = " + a);
    </script>
</body>

</html>